¹Pin, C.,²Gannoun, A.
Journal of Analytical Atomic Spectroscopy 34, 2136-2146 Link to Article [DOI: 10.1039/c9ja00272c]
¹Géologie, CNRS, Université Clermont-Auvergne, Campus des Cézeaux, 6 avenue Blaise Pascal, Aubière Cedex, 63 178, France
²Laboratoire Magmas et Volcans, Université Clermont Auvergne, CNRS, UMR 6524, OPGC-IRD, Clermont-Ferrand, F-63000, France

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¹Alexeev, V.A.,²Bagulya, A.V.,^2,3,4Volkov, A.E.,²Gippius, A.A.,²Goncharova, L.A.,²Gorbunov, S.A.,⁶Grachev, V.M.,³Dashkina, A.B.,¹ Kalinina, G.V.,^2,5Konovalova, N.S.,^2,5Okateva, N.M.,¹Pavlov,¹T.A.,^2,5,6Polukhina, N.,^2,5Starkov, N.I.,²Soe, T.N.,²Chernyvsky, M.M.,^2,5Shchedrina, T.V.
Bulletin of the Lebedev Physics Institute 46, 251-255 Link to Article [DOI: 10.3103/S1068335619080037]
¹Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, 19 Kosygina St., Moscow, 119991, Russian Federation
²Lebedev Physical Institute, Russian Academy of Sciences, 53 Leninskii Pr., Moscow, 119991, Russian Federation
³Russian Scientific Center “Kurchatov Institute”, 1 Kurchatova Sq., Moscow, 123182, Russian Federation
⁴Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research, 6 Joliot-Curie St., Dubna, Moscow Region, 141980, Russian Federation
⁵National University of Science and Technology “MISIS”, 4 Leninskii Pr., Moscow, 119049, Russian Federation
⁶National Research Nuclear University “MEPhI”, 31 Kashirskoe Sh., Moscow, 115409, Russian Federation

¹Kanzaki, M.
Journal of Mineralogical and Petrological Sciences 114, 214-218 Link to Article [DOI: 10.2465/jmps.190414]
¹Institute for Planetary Materials, Okayama University, Misasa, Tottori, 682-0193, Japan

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^1,2Edey, D.R.,¹Pollmann, S.I.,^1,3Lorusso, D.,^1,4,5Drangova, M.,²Flemming, R.L.,^1,4,5Holdsworth, D.W.
Journal of X-ray Sciences and Technology 27, 919-934 Link to Article [DOI: 10.3233/XST-190511]
¹Imaging Research Laboratories, Robarts Research Institute, Schulich School of Medicine Dentistry, Western University, London, ON, Canada
²Department of Earth Sciences, Western University, London, ON, Canada
³Department of Physiology and Pharmacology, Schulich School of Medicine Dentistry, Western University, London, ON, Canada
⁴Department of Surgery, Schulich School of Medicine Dentistry, Western University, London, ON, Canada
⁵Department of Medical Biophysics, Schulich School of Medicine Dentistry, Western University, London, ON, Canada

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¹H.Lammer,^1,2M.Leitzinger,¹M.Scherf,^1,2P.Odert,³C.Burger,¹D.Kubyshkina,³C.Johnstone,³T.Maindl,⁴C.M.Schäfer,³M.Güdel,^5,6N.Tosi,^5,6A.Nikolaou,⁷E.Marcq,^8,9N.V.Erkaevh,¹⁰L.Noack,¹K.G.Kislyakovac,¹L.Fossati,³E.Pilat-Lohinger,³F.Ragossnig,³E.A.Dorfi
Icarus (in Press) Link to Artice [https://doi.org/10.1016/j.icarus.2019.113551]
¹Space Research Institute, Austrian Academy of Sciences, Graz, Austria
²Institute of Physics/IGAM, University of Graz, Austria
³Department of Astrophysics, University of Vienna, Austria
⁴Institute of Astronomy and Astrophysics, University of Tübingen, Germany
⁵Institute of Planetary Research, Department of Planetary Physics, DLR, Berlin Germany
⁶Department of Astronomy and Astrophysics, Berlin Institute of Technology, Germany
⁷LATMOS, Université de Versailles Saint-Quentin-en-Yvelines, Guyancourt, France
⁸Institute of Computational Modelling SB RAS, Krasnoyarsk, Russian Federation
⁹Siberian Federal University, Krasnoyarsk, Russian Federation
¹⁰Department of Earth Sciences, Freie Universität Berlin, Germany
Copyright Elsevier

The atmospheric noble gas isotope and elemental bulk ratios on Venus and Earth provide important information on their origin and evolution. If the protoplanets grew to a certain mass (i.e. > 0.5 M_Earth), they could have captured H₂-dominated primordial atmospheres by accreting gas from the circumstellar disk during the formation of the Solar System, which were then quickly lost by hydrodynamic escape after the disk dissipated. In such a case, the EUV-driven hydrodynamic flow of H atoms dragged heavier elements with it at different rates, leading to changes in their initial isotope ratios. For reproducing Earth and Venus present atmospheric ³⁶Ar/³⁸Ar, ²⁰Ne/²²Ne, ³⁶Ar/²²Ne, isotope and bulk K/U ratios we applied hydrodynamic upper atmosphere escape and Smooth Particle Hydrodynamics (SPH) impact models for the calculation of captured H₂-dominated primordial atmospheres for various protoplanetary masses. We investigated a wide range of possible EUV evolution tracks of the young Sun and initial atmospheric compositions based on mixtures of captured nebula gas, outgassed and delivered material from ureilite, enstatite and carbonaceaous chondrites. Depending on the disk lifetime of ≈ 3-5 Myr (Bollard et al., 2017; Wang et al., 2017) and the composition of accreted material after disk dispersal, we find from the reproduction of the present atmospheric Ar, Ne, and bulk K/U ratios, that early Earth’s evolution can be explained if proto-Earth had accreted masses between ≈ 0.53 − 0.58 M_Earth by the time the nebula gas dissipated. If proto-Earth would have accreted a higher mass during the disk lifetime the present atmospheric Ar and Ne isotope ratios can not be reproduced with our model approach. For masses > 0.75M_Earth, Earth would have had a problem to get get rid of its primordial atmosphere. If proto-Earth accreted ≈ 0.53 − 0.58M_Earth of enstatite-dominated material as suggested by Dauphas (2017) during the disk lifetime, it would have captured a tiny primordial atmosphere that was lost ≈3 Myr after the disk dissipated. In such a case we find that the present-day atmospheric Ar and Ne isotope ratios can be best reproduced if the post-nebula impactors contained ≈ 5% weakly depleted carbonaceous chondritic material and ≈ 95% enstatite chondrites that are strongly depleted in Ar, Ne and moderately volatile elements like potassium. If higher amounts of carbonaceous chondrites were involved in early Earth’s accretion as recently suggested by Schiller et al. (2018), then the Earth’s present atmospheric Ar and Ne ratios can only be reproduced if the involved carbonaceous chondritic post-nebula material was also highly depleted in these noble gases and/or had to be partially be delivered as long as the primordial atmosphere was yet escaping. As long as primordial atmospheres surround the growing protoplanets the abundance of their volatile elements is overwritten by their respective captured solar-like atmospheric abundances. Therefore the initial composition of the protoplanets at the disk dispersal time can not be identified by our method. For masses less than 0.5 M_Earth atmospheric escape cannot explain the present-day ratios, i.e. if Earth grew slower then these ratios have to be explained differently (Marty, 2012). If proto-Venus captured a primordial atmosphere it should have grown to masses of ≈ 0.8 − 1.0 M_Venus during the time until the disk dissipated and if early Venus accreted its main mass during the disk lifetime than the present atmospheric Ar and Ne isotope ratios and the observed K/U ratios on Venus surface can also be reproduced by the escape of a captured primordial atmosphere that is lost within ≤ 100 Myr, if the Sun was born between a weakly and moderately active young G star. New precise re-measurements of atmospheric noble gases are necessary by future Venus missions to better constrain the material that was involved in the planet’s accretion history and possibly also the EUV activity evolution of the young Sun. In addition, measurements of other moderately volatile element and isotope ratios on the surface such as Rb/U, ⁶⁴Zn/⁶⁶Zn, and ³⁹K/⁴¹K can give an insight on whether Venus accreted slow or fast, i.e. almost to its final mass within the disk lifetime.

¹E. Palomba,¹E. D’Aversa,^2,3T. M. Sato,^1,4A. Longobardo,¹F. Dirri,^5,6S. Aoki,⁷G. Orton,¹G. Sindoni,¹F. Oliva,¹G. Carrozzo,⁸Y. Kasaba
The Astrophysical Journal, Letters 882, L22 Link to Article [DOI
https://doi.org/10.3847/2041-8213/ab339e]
¹INAF-IAPS, via del Fosso del Cavaliere 100, I-00133 Rome, Italy
²ISAS-JAXA, Sagamihara, Kanagawa 252-5210, Japan
³Hokkaido Information University, Ebetsu, Hokkaido 069-8585, Japan
⁴DIST-Università Parthenope, Centro Direzionale Isola C4, 80143, Naples, Italy
⁵Planetary Aeronomy, Royal Belgian Institute for Space Aeronomy, 3 av. Circulaire, B-1180 Brussels, Belgium
⁶Fonds National de la Recherche Scientifique, rue d’Egmont 5, B-1000 Brussels, Belgium
⁷NASA/Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA
⁸Planetary Plasma and Atmospheric Research Center, Graduate School of Science, Tohoku University, Sendai, Miyagi 980-8578, Japan

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^1,2Lionel G. Vacher,¹Maxime Piralla,³Matthieu Gounelle,⁴⁵Martin Bizzarro,¹Yves Marrocchi
The Astrophysical Journal, Letters 882, L20 Link to Article [DOI
https://doi.org/10.3847/2041-8213/ab3bd0]
¹CRPG, CNRS, Université de Lorraine, UMR 7358, Vandoeuvre les Nancy, F-54501, France
²Department of Physics, Washington University, St. Louis, MO, USA
³IMPMC, MNHN, UPMC, UMR CNRS 7590, 61 rue Buffon, F-75005 Paris, France
⁴Centre for Star and Planet Formation and Natural History Museum of Denmark, University of Copenhagen, DK-1350 Copenhagen, Denmark

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^1,2K. J. Mathew,¹K. Marti
The Astrophysical Journal, Letters 882, L17 Link to Article [DOI
https://doi.org/10.3847/2041-8213/ab357b]
¹Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, CA 92093, USA
²Actinide Analytical Chemistry, Los Alamos National Lab, MS G740, Los Alamos, NM 87545, USA

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^1,2Shiyong Liao,¹Weibiao Hsu,¹Ying Wang,¹Ye Li,²Chipui Tang,²Bao Mei
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13408]
¹CAS Center for Excellence in Comparative Planetology, Purple Mountain Observatory, Nanjing, 210034 China
²State Key Laboratory for Lunar and Planetary Sciences, Macau University of Science and Technology, Taipa, Macau
Published by arrangement with John Wiley & Sons

Eucrites represent one of the major lithologies of the Vestan upper crust, which had experienced pervasive and intense thermal metamorphism. To better constrain the timing and mechanism of thermal metamorphism, we carried out in situ Pb‐isotope analysis of an unbrecciated basaltic eucrite NWA 6594 on the basis of detailed mineralogical and petrographic investigations. Zircon Pb‐Pb dating reveals that NWA 6594 emplaced before or at 4547 ± 11 Ma (95% confidence, MSWD = 1.3). Studies of silica minerals indicate that NWA 6594 had experienced intense thermal metamorphism after emplacement, followed by a late impact reheating and rapid cooling. Apatite grains yield a weighted mean Pb‐Pb age of 4523 ± 2 Ma (95% confidence, MSWD = 0.76). This age could not be attributed to slow cooling after the initial crystallization, but most likely related to an independent thermal event that induced thermal metamorphism. The protracted time lag (~24 ± 13 Myr) between zircon and apatite closure ages indicates that this thermal event is most probably induced by an intense impact event that was synchronous with the metal–silicate mixing event recorded by mesosiderites. HEDs may have experienced multiple stages of thermal metamorphism after emplacement. The late impact reheating occurred after thermal metamorphism, which caused crystallization of tridymite.

¹Jan Leitner,²Knut Metzler,³Christian Vollmer,⁴Christine Floss,⁴Pierre Haenecour,¹János Kodolányi,⁵Dennis Harries,¹Peter Hoppe
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13412]
¹Max Planck Institute for Chemistry, Particle Chemistry Department, Hahn‐Meitner‐Weg 1, 55128 Mainz, Germany
²Institute for Planetology, University of Münster, 48149 Münster, Germany
³Institute for Mineralogy, University of Münster, 48149 Münster, Germany
⁴Laboratory for Space Sciences, Physics Department and McDonnell Center for Space Sciences, Washington University in St. Louis, One Brookings Drive, St. Louis, Missouri, 63130 USA
⁵Institute of Geoscience, Friedrich Schiller University Jena, Carl‐Zeiss‐Promenade 10, 07745 Jena, Germany
Published by arrangement with John Wiley & Sons

We investigated the inventory of presolar silicate, oxide, and silicon carbide (SiC) grains of fine‐grained chondrule rims in six Mighei‐type (CM) carbonaceous chondrites (Banten, Jbilet Winselwan, Maribo, Murchison, Murray and Yamato 791198), and the CM‐related carbonaceous chondrite Sutter’s Mill. Sixteen O‐anomalous grains (nine silicates, six oxides) were detected, corresponding to a combined matrix‐normalized abundance of ~18 ppm, together with 21 presolar SiC grains (~42 ppm). Twelve of the O‐rich grains are enriched in ¹⁷O, and could originate from low‐mass asymptotic giant branch stars. One grain is enriched in ¹⁷O and significantly depleted in ¹⁸O, indicative of additional cool bottom processing or hot bottom burning in its stellar parent, and three grains are of likely core‐collapse supernova origin showing enhanced ¹⁸O/¹⁶O ratios relative to the solar system ratio. We find a presolar silicate/oxide ratio of 1.5, significantly lower than the ratios typically observed for chondritic meteorites. This may indicate a higher degree of aqueous alteration in the studied meteorites, or hint at a heterogeneous distribution of presolar silicates and oxides in the solar nebula. Nevertheless, the low O‐anomalous grain abundance is consistent with aqueous alteration occurring in the protosolar nebula and/or on the respective parent bodies. Six O‐rich presolar grains were studied by Auger Electron Spectroscopy, revealing two Fe‐rich silicates, one forsterite‐like Mg‐rich silicate, two Al‐oxides with spinel‐like compositions, and one Fe‐(Mg‐)oxide. Scanning electron and transmission electron microscopic investigation of a relatively large silicate grain (490 nm × 735 nm) revealed that it was crystalline åkermanite (Ca₂Mg[Si₂O₇]) or a an åkermanite‐diopside (MgCaSi₂O₆) intergrowth.